Hydrogen atoms play a pivotal role in achieving superlubricity in DLC films. Nevertheless, the inherent limitations in analytical testing techniques obscure the mechanisms by which hydrogen atoms achieve superlubricity in DLC films. Furthermore, direct evidence supporting the widely accepted mechanism of hydrogen passivation remains elusive. Therefore, we used ReaxFF MD simulations to investigate the effects of different hydrogen content on the tribological and wear properties of hydrogen-doped H-DLC films. Hydrogen atoms diffuse from the DLC films and gradually accumulate on the friction surface during the sliding, effectively passivating and inhibiting the C–C bonds at the interface. This reduces cross-linking between H-DLC films, consequently loweringfrictiontemperature significantly during the sliding. A significant release of hydrogen atoms during the friction process weakens the strength of machinery of H-DLC films, potentially causing structural failures under hydrogen-rich conditions, with the released hydrogen atoms subsequently occupying structural voids within films. At the microscopic scale, the friction of H-DLC film decreases with the increase of hydrogen content, but when the hydrogen content reaches 40 % or above, the local collapse of the system will be caused, resulting in the failure of superlubricity. Finally, the friction and wear of H-DLC film under high hydrogen conditions will rebound.

中文翻译：

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不同氢含量对H-DLC薄膜超润滑性能的原子效应及机理


氢原子在 DLC 薄膜中实现超润滑性方面起着关键作用。然而，分析测试技术的固有局限性掩盖了氢原子在 DLC 薄膜中实现超润滑性的机制。此外，支持广泛接受的氢钝化机制的直接证据仍然难以捉摸。因此，我们使用 ReaxFF MD 模拟来研究不同氢含量对氢掺杂 H-DLC 薄膜的摩擦学和磨损性能的影响。氢原子从 DLC 膜中扩散，并在滑动过程中逐渐积累在摩擦表面上，有效地钝化和抑制界面处的 C-C 键。这减少了 H-DLC 薄膜之间的交联，从而显著降低了滑动过程中的摩擦温度。在摩擦过程中，氢原子的大量释放会削弱 H-DLC 薄膜机械的强度，在富氢条件下可能导致结构失效，释放的氢原子随后占据薄膜内的结构空隙。在微观尺度上，H-DLC 膜的摩擦力随着氢含量的增加而减小，但当氢含量达到 40 % 或以上时，会引起体系的局部崩溃，导致超润滑性失效。最后，H-DLC 薄膜在高氢条件下的摩擦和磨损会反弹。